This invention generally relates to a coupling device for connecting lines between relatively rotating members, and more particularly to a coupling device for directing the passage of lines between a non-rotating antenna base structure and a rotating antenna which provides increased rotational travel while minimizing stress on the lines.
In the field of large rotating antennas, a problem exists in supplying the large number of lines, such as cables and hoses, between the steerable antenna and the non-moving base. If a cable is routed directly on the azimuth axis, then antenna motion imposes only twisting along the cable, without the cable having to follow the arc traced by a point off the axis. Thus, the more central the cable location, the more gentle the cable motion during rotation and therefore, the less the cable will wear. As a result, a common practice is to run all lines through the central hole in the main bearing axis of the antenna. Although these large scale antennas have very large diameter center holes, the center hole can be crowded with many cables, hoses and power connections, plus an encoder drive shaft for the azimuth angle encoder. Typically, the antenna is designed such that the center area of the center hole houses the encoder drive shaft, the next concentric layer houses the electrical cables and coaxial cables and the outermost layer within the center hole houses the cooling hose connections. That design segregates each of the three functional groups to protect the sensitive high-voltage cables and the encoder drive shaft from contact with the cooling water hoses. The electrical cabling associated with the antenna is afforded as long a length as possible within the structure on which the antenna is mounted in order to reduce the severity of bending and twisting imparted to the cables.
However, the cooling hoses, which in some cases can be on the order of 5xe2x80x3 in diameter, cannot tolerate any twists along their axes. Therefore, a device is needed which handles the cooling hoses in such a way as to allow the antenna to be rotated at least 440xc2x0 without unduly twisting, bending or otherwise stressing the cooling hoses.
Some prior art arrangements which attempt to address this problem include a flat spiral, a flat bend with swivels, a vertical drape with swivels, and a flat coil with vertical drape for slack take-up. The flat spiral looks like a watch spring, and winds and unwinds the hose to follow the antenna motion. However, to obtain the required 440xc2x0 of minimum travel, a hose length of roughly 100 times the hose diameter is required when using the flat spiral arrangement. The flat bend arrangement and the vertical drape arrangement both require increased floor space around the axis of the antenna to accommodate the slack which is produced in the hose as the antenna rotates, and both arrangements require the use of swivel end connections to negate twisting of the hose. These connections, however, tend to leak thus reducing the reliability of the swivel end connection arrangement. The flat coil with vertical drape for slack take-up arrangement is a variation of the flat spiral in which the spiral stays tight against the rotating housing, and pays out or reels in the hose on a tangent as the antenna rotates. The surplus hose is collected in a vertical drape, the length of which changes to maintain some tension on the spiral. This arrangement has no swivel end connections, but unfortunately requires excessive hose lengths and increased floor space around the housing of the antenna.
It is therefore an object of this invention to provide an improved device for coupling one or more lines between relatively rotating structures.
It is a further object of this invention to provide such a coupling device which requires a minimum length of the lines and a minimum of operating area.
It is a further object of this invention to provide such a coupling device which effectively reduces or eliminates twisting, bending and tension in the lines.
It is yet a further object of the invention to provide such a coupling device which enables increased travel of a rotating antenna.
The invention results from the realization that a coupling apparatus for coupling a line including cables, conduits and the like between rotatable members capable of limited relative rotation which enables increased travel while minimizing twisting, bending and tension to avoid fatigue can be achieved by connecting the line between the two relatively rotatable members and using a guide to reverse direction of the line between those members so that it wraps the lines around the members in opposite directions to maintain slack control of the line.
This invention features a coupling apparatus including first and second relatively rotatable members, a first line fixed with a first of the relatively rotatable members and wrapped around it in a first direction, a guide revolvable about the relatively rotatable members for reversing direction of the first line to the second relatively rotatable member, the line being wrapped around the second relatively rotatable member in the opposite direction and fixed with it and a drive mechanism for rotating the guide for maintaining a slack control of the line between the relatively rotatable members.
In a preferred embodiment, the drive mechanism may include a second line fixed with each of the first and second relatively rotatable members and wrapped around them in the opposite direction from the first line and the guide reverses direction of the second line between the first and second relatively rotatable members. The guide may revolve at less than the speed of relative rotation between the relatively rotatable members, the speed of the guide being a function of the ratio of the radii of the first and second relatively rotatable members. The guide may include a bearing device mounted on one member and a second bearing device mounted on the other member. The line may include a conduit or a cable. The guide may include a curved track which may be xe2x80x9cCxe2x80x9d shaped. The curved track may include at least one roller or it may include a low friction element.
The invention also features a coupling device including first and second relatively rotating members mounted about a common axis, first and second lines fixed between the first and second members, the first line being adapted to wrap around the first member in a first direction and around the second member in a second direction, opposite the first direction, the second line being adapted to wrap around the first member in the second direction and around the second member in the first direction and a guide revolvably mounted between the first and second members for translating the first and second lines between the first member and the second member as the first and second members rotate relative to each other.
In a preferred embodiment, the guide may include first and second opposing pulley devices, the first pulley device translating the first line between the first and second members and the second pulley device simultaneously translating the second line between the first and second members. The first and second pulley devices may change the direction of the first and second lines respectively, as they are translated between the first and second members. When the second member rotates in the first direction relative to the first member, the guide may translate the first line from the second member to the first member and the second line from the first member to the second member. When the second member rotates in the second direction relative to the first member, the guide may translate the first line from the first member to the second member and the second line from the second member to the first member.
This invention also features a coupling device including first and second relatively rotating members mounted to rotate about a common axis, a first line fixed between the first and second members, the first line being adapted to wrap around the first member in a first direction and around the second member in a second direction, opposite the first direction, a guide revolvably mounted to the first and second members for translating the first line between the first and second members, as the first and second members rotate relative to each other and a drive mechanism for revolving the guide around the common axis at a rate which is less than the relative rate of rotation of the first and second members.
In a preferred embodiment, the guide may reverse the direction of the first line from the first direction to the second direction as it translates the first line from the first member to the second member. The drive mechanism may include a second line fixed between the first and second members, the second line being adapted to wrap around the first member in the second direction and around the second member in the first direction, the guide translating the second line between the first and second members as the first and second members rotate relative to each other. The guide may reverse the direction of the second line from the second direction to the first direction as it translates the second line from the first member to the second member. The guide may include a first pulley device for reversing the direction of the first line and the may guide include opposing pulley devices for simultaneously reversing the direction of the first and second lines. The first and second members each may include a flange for supporting the first line as it is wrapped around the first and second members.